Sidebar by Martha Quillen
Geology – April 2005 – Colorado Central Magazine
Upon reading this story, we suggested a little more detail about just how likely, or unlikely, it was that earthquakes will be coming to an area near you. But the author was disinclined to speculate. Apparently, even a geologist can’t predict when an earthquake will happen.
Furthermore, our region presents some challenges for experts evaluating the likelihood of quakes. According to the U.S.G.S. website, “Colorado is considered a region of minor earthquake activity, although there are many uncertainties because of the very short time period for which historical data is available. The northwestern and southwestern corners, and the Sangre de Cristo Mountains in the south-central section of the State, have had no activity in historic times.”
But there have been some earthquakes in our region over the years:
On November 15, 1901 a quake rolled boulders onto the highway in Buena Vista, cracked windows, and agitated the water in Cottonwood Lake.
In 1955, a strong earthquake cracked chimneys and ground in Lake City.
On October 11, 1960, a quake cracked a foundation and loosened cupboards from walls in Montrose.
In 1979, a small (2.9) tremor was centered near Florissant and Lake George, and resulted in damage reports in Cripple Creek and Royal Gorge.
In 1983, a minor quake hit a sparsely populated area south of Montrose, and was felt in Cimarron.
On March 16, 1985, a quake, magnitude 3.3, centered northeast of Salida and was felt in Salida and Nathrop.
On September 3, 1986, a quake, magnitude 3.5, was centered northwest of Crested Butte and felt in Gunnison.
Of course, Central Colorado’s seismic adventures seem very modest compared to the weekly, and sometimes daily, mini-trembling common in New Madrid, Missouri, the home of what’s often cited as the country’s worst earthquakes, which happened in 1811 and 1812; or if you reflect upon the 17 earthquakes of over 3.0 magnitude (3.0 is commonly cited as a division point between lesser and greater shakes) which happened last week alone in Alaska.
But in regard to our region’s relative calm, Paul Martz pointed out that quakes happen when stress builds up enough to cause movement along a fault, and a long period of quiescence may indicate that stress has not been relieved. Due to the number of faults in our area and their relatively recent movement in geologic terms, he thinks that earthquakes are an inevitable eventuality, but he won’t speculate on whether that’s more likely to be soon, or in decades, or in a 100 years, or 500. It could happen any time, he says.
So is there anything we should do about that?
Paul didn’t feel comfortable addressing that question, either. But he does think it would be better if people didn’t put their houses on faults and under potential mud slides. As he sees it, Colorado’s faults should be identified (which is done by geologic mapping), so that people can avoid building on them. But there are restrictions to discourage construction in flood plains, avalanche zones, rock slide paths, and the like, and Coloradans frequently build on those sites anyway. So….
One of the most alarming things about earthquakes, according to Encyclopedia Britannica, is that the regions most known for them don’t necessarily have more earthquakes. Instead they have more vulnerable structures.
But there are problems in establishing building codes which increase earthquake safety in a region that’s been relatively stable seismically. After a recent San Francisco earthquake, it was mentioned that the historic brick buildings built in the nineteenth century were particularly susceptible to damage, and yet such buildings are our pride and joy here in Central Colorado.
And there’s also cost efficiency to consider. Depending upon their exact location, local residents with limited funds may be wiser to invest more to protect against wildfire — or snowload.
Considering all of the precautionary news shows and disaster movies which warn against everything from virulent African viruses to terrorist attacks, it would be nice to be able to say, unequivocally, that there is little or no danger from earthquakes in our area. Or presuming that’s not true, it would be nice to announce what precautions should be taken to prevent damage in the event of a shake.
But real earthquakes aren’t as predictable as Hollywood disasters. And real people seldom have the money to guard against all of the possible calamities which may be headed their way.
–Martha Quillen